卡宾类化合物反应机理的理论研究

发布时间：2018-06-10 20:36

本文选题：密度泛函理论 + 氨基金卡宾　；参考：《曲阜师范大学》2017年硕士论文

【摘要】：近年来,随着环境污染问题的日益加重以及地球资源的不断消耗枯竭,发展新型的催化反应、实现物质的绿色转换已成为当前化学工作者研究的重点和前沿领域。因此,要完善和发展新型的催化反应,必须进一步加深对相关催化反应机理的认识和理解。本论文基于量子化学计算理论对反应能量以及几何结构的研究,深化了对反应机理的理解,并对相关反应的设计提供了理论依据。本论文的主要工作包括以下三个方面:(1)利用密度泛函理论研究了通过环化重排反应合成一价氨基金卡宾化合物的反应机理。计算结果表明经过[3,3]-σ重排过程的反应机制相对于1,2-烷基迁移的机理更为有利,这主要是由于1,2-烷基迁移过程会产生很强的空间位阻作用造成的。[3,3]-σ重排过程为整个反应的决速步骤。通过分析不同取代基反应决速步骤过渡态的空间结构发现,影响产率的主要因素在于不同取代基所产生的空间效应。(2)基于密度泛函理论研究了氮杂环卡宾类化合物(NHCs)催化的安息香缩合反应详细的反应机理。计算结果表明第一次的氢迁移过程是在溶剂中水分子的协助下完成的,第二次的氢迁移经历的是一个协同过程而并非分步机理。此外,我们挖掘了反应中产生化学选择性的理论根源:不同催化剂结构上的差异所导致的空间位阻作用。(3)运用密度泛函理论研究了氮杂环卡宾类化合物(NHCs)催化二烯醛和偶氮烯烃发生[4+3]和[4+1]环化反应的机理。研究发现添加剂在质子转移和脱水过程中起了至关重要的作用。通过扭曲变形相互作用能分析了催化剂和底物取代基对区位选择性的影响。对NHC-A催化、R2’上取代基为Boc的反应A而言,导致产生区位选择性的主要因素是过渡态TS3A和TS8A中3与R2’之间的相互作用造成的。对NHC-B催化、R2’上取代基为Boc的反应B而言,区位选择性的产生主要是由于催化剂NHC-B中不稳定的船式构象和稳定的椅式构象的差异而导致的。对NHC-A催化、R2’上取代基为Ts的反应C而言,TS3C和TS6C中3与R2’的变形作用是导致区位选择性相对于反应A增强的主要原因。
[Abstract]:In recent years, with the worsening of environmental pollution and the depletion of the earth's resources, the development of new catalytic reactions to achieve the green conversion of substances has become the focus and frontier of chemical research. Therefore, in order to perfect and develop the new catalytic reaction, we must further understand the mechanism of the catalytic reaction. Based on the quantum chemical calculation theory, the study of the reaction energy and geometric structure has deepened the understanding of the reaction mechanism and provided the theoretical basis for the design of the related reactions. The main work of this thesis includes the following three aspects: 1) the mechanism of the synthesis of monovalent ammonium-fund carbene compounds by cyclization rearrangement reaction is studied by using density functional theory (DFT). The calculated results show that the reaction mechanism of [3N3]-蟽 rearrangement process is more favorable than that of the 1 ~ (2 +) -alkyl migration process. This is mainly due to the strong steric hindrance in the migration process of 1 ~ (2 +) -alkyl group. [3]-蟽 -rearrangement process is the critical step of the whole reaction. By analyzing the spatial structure of the transition states in different substituent reaction, The main factor affecting yield is the spatial effect of different substituents. (2) based on density functional theory, the detailed reaction mechanism of benzoin condensation catalyzed by heterocyclic carbenes was studied. The results show that the first hydrogen migration process is completed with the help of water molecules in the solvent, and the second hydrogen migration is a synergistic process rather than a stepwise mechanism. In addition, We have explored the theoretical origin of chemical selectivity in the reaction: the steric effect caused by the difference in the structure of different catalysts. (3) using density functional theory, we have studied the catalytic properties of dienal and dienal by using the density functional theory (DFT) of nitrogen heterocyclic carbenes (NHCs). Mechanism of [43] and [41] cyclization of azo olefins. It is found that additives play an important role in proton transfer and dehydration. The influence of catalyst and substrate substituent on location selectivity was analyzed by means of distorted deformation interaction energy. For NHC-A catalyzed reaction A with substitution group Boc, the main factor leading to site selectivity is the interaction between 3 and R2'in the transition state TS3A and TS8A. For the reaction B on NHC-B catalyst with substitution group Boc, the location selectivity is mainly due to the difference of unstable ship-type conformation and stable chair conformation in NHC-B catalyst. The deformation of 3 and R2'in TS3C and TS6C is the main reason for the enhancement of location selectivity relative to reaction A.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.12

【相似文献】